ceph-volume: systemd: create systemd entry point script

Signed-off-by: Alfredo Deza <adeza@redhat.com>

src/ceph-volume/ceph_volume/systemd.py

@@ -0,0 +1,87 @@
+"""
+This file is used only by systemd units that are passing their instance suffix
+as arguments to this script so that it can parse the suffix into arguments that
+``ceph-volume <sub command>`` can consume
+"""
+
+import sys
+import logging
+from ceph_volume import log
+from ceph_volume import process
+
+log.setup(name='ceph-volume-systemd.log')
+logger = logging.getLogger('systemd')
+
+
+class SuffixParsingError(SystemExit):
+
+    def __init__(self, suffix, part=None):
+        self.suffix = suffix
+        self.part = part
+        SystemExit.__init__(self, self.__str__())
+
+    def __str__(self):
+        return 'Unable to parse the %s from systemd suffix: %s' % (self.part, self.suffix)
+
+
+def parse_subcommand(string):
+    subcommand = string.rsplit('-', 1)[-1]
+    if not subcommand:
+        raise SuffixParsingError('subcommand', string)
+    return subcommand
+
+
+def parse_osd_id(string):
+    osd_id = string.split('-', 1)[0]
+    if not osd_id:
+        raise SuffixParsingError('OSD id', string)
+    return osd_id
+
+
+def parse_osd_uuid(string):
+    osd_id = '%s-' % parse_osd_id(string)
+    osd_subcommand = '-%s' % parse_subcommand(string)
+    # remove the id first
+    trimmed_suffix = string.split(osd_id)[-1]
+    # now remove the sub command
+    osd_uuid = trimmed_suffix.split(osd_subcommand)[0]
+    if not osd_uuid:
+        raise SuffixParsingError('OSD uuid', string)
+    return osd_uuid
+
+
+def main(args=None):
+    """
+    Main entry point for the ``ceph-volume-systemd`` executable. ``args`` are
+    optional for easier testing of arguments.
+
+    Expected input is similar to::
+
+        ['/path/to/ceph-volume-systemd', '<osd id>-<osd uuid>-<device type>']
+
+    For example::
+
+        [
+            '/usr/bin/ceph-volume-systemd',
+            '0-8715BEB4-15C5-49DE-BA6F-401086EC7B41-lvm'
+        ]
+
+    The last part of the argument is the only interesting bit, which contains
+    the metadata needed to proxy the call to ``ceph-volume`` itself.
+
+    Reusing the example, the proxy call to ``ceph-volume`` would look like::
+
+        ceph-volume lvm 0 8715BEB4-15C5-49DE-BA6F-401086EC7B41
+
+    """
+    args = args or sys.argv
+    suffix = args[-1]
+    sub_command = parse_subcommand(suffix)
+    osd_id = parse_osd_id(suffix)
+    osd_uuid = parse_osd_uuid(suffix)
+    logger.info('raw systemd input received: %s', suffix)
+    logger.info('osd id: %s, osd uuid: %s, sub-command: %s', osd_id, osd_uuid, sub_command)
+    command = ['ceph-volume', sub_command, 'activate', osd_id, osd_uuid]
+
+    # don't log any output to the terminal, just rely on stderr/stdout going to logging
+    process.run(command, terminal_logging=False)